1. Technical Field
The present disclosure relates generally to the treatment of respiratory conditions with continuous positive airway pressure (CPAP) devices, and more particularly, to detection of patient interface disconnect for controlling CPAP therapy.
2. Related Art
Sleep apnea is a serious medical condition in which patient breathing during sleep pauses abnormally, or is abnormally low. Apnea is categorized as obstructive, central, and combined obstructive and central, though the obstructive sleep apnea (OSA) is the most common. The patient's upper airway repeatedly narrows or collapses, causing pauses in breathing that may extend in duration up to half a minute. Although some degree of apnea is considered normal, in more severe cases, daytime sleepiness and fatigue may result as a consequence of reduced blood oxygen saturation, as well as constant interruptions to sleep cycles because of patients gasping for air. There have been studies linking sleep apnea to more severe long-term health issues including heart disease and depression, and recently, to cancer as well. With apnea being strongly linked to obesity, and with obesity being projected to increase, the number of patients suffering from sleep apnea is likely to increase concomitantly.
One common treatment for obstructive sleep apnea is continuous positive airway pressure (CPAP) therapy, where a positive pressure is applied to the patient to prevent its collapse as would otherwise occur during an apnea episode. By retaining the patient's airway, normal, uninterrupted breathing during sleep is ensured. In a basic implementation, CPAP therapy applies a constant pressure that is not tied to the patient's normal breathing cycle. The positive airway pressure is desired in the inspiratory phase when the pressure differences between the lungs and the nose contribute to the collapse of the intermediate airway.
Earlier patient breathing assistance devices tended to be uncomfortable to use because of the bulkiness associated with the patient interface, as well as the misapplication of pressure resulting from sub-optimal control methodologies. The application of pressure, no matter how slight, against respiratory efforts of the patient can cause a sense of asphyxiation because of the corresponding increase in work of breathing that can be sufficiently distracting to cause difficulties for the patient to fall asleep. Various improvements have been developed to reduce discomfort to the patient during therapy, particularly at critical points along the respiratory cycle. Thus, a therapeutic device that was previously prescribed only for the more severe cases of sleep apnea in which the benefits of treatment outweighed the significant discomfort is now useful for treating a wider spectrum of sleep apnea conditions. Notwithstanding the increased availability of CPAP devices for home use as a result of these technical improvements, ensuring patient compliance with the prescribed treatment has remained a challenge.
Patient comfort or rather, the lack thereof, was not the sole reason for reduced CPAP treatment compliance. The constant high frequency hissing noise of air flowing back and forth from the CPAP device, the patient interface, and the connecting conduits, was and remains a frequent complaint of not only the patient, but of the patient's partners as well. Deliberate efforts have been undertaken to solve the noise issues with improved blowers and sound insulation features integrated into the patient interface and other gas passage conduits.
To a large extent, conventional CPAP devices are quiet when operating normally, that is, with the patient wearing the interface and is correctly connected to the CPAP device with minimal leakage. However, when any part is disconnected, a substantial amount of noise is generated while the CPAP device continues to operate and the blower continues to generate airflow. Although ideally the patient will experience continuous and uninterrupted sleep, this is oftentimes not the case. The patient may need to disconnect from the CPAP device for any number of reasons such as bathroom breaks, getting a drink of water, and so forth. Typically, such disconnections occur while the patient is not fully awake, and therefore may not have an awareness or mental faculty to turn off the CPAP device. Furthermore, the patient interface may also be disconnected unintentionally during sleep.
Outside of the clinical environment where a shared sleeping arrangement is common, the sleeping partner may be roused awake from the excessive noise. Accordingly, there is a need in the art for detecting patients disconnecting from the CPAP device circuit, and in response to detecting such condition, deactivating the CPAP device so that no further airflow noise is generated.